Preparation of 5-ethylidenebicyclo(2.2.1)hept-2-enes

ABSTRACT

5-Vinylbicyclo(2.2.1)hept-2-enes heated in the presence of a titanium catalyst system are isomerized to 5ethylidenebicyclo(2.2.1)hept-2-enes. The catalyst system of this invention comprises a titanium compound, an alkali metal, and a cyclopentadienyl magnesium halide. The catalyst system is highly efficient and capable of rapidly isomerizing 5vinylbicyclo(2.2.1)hept-2-enes. 5-Ethylidenebicyclo(2.2.1)hept-2enes are useful comonomers for polymerization with Alpha olefins such as ethylene and propylene.

United States Patent [151 3,696,157 Schneider Oct. 3, 1972 [54] PREPARATION OF 5- 3,535,396 10/1970 Schneider ..260/666 PY ETHYLIDENEBICYCLO(2.2.l)HEPT-2- 3,538,171 11/1970 Schneider ..260/666 PY ENES 3,535,961 2/1971 Nagase et a1. ..260/666 FY [72] Inventor: Wolfgang Schneider Brecksvme 3,594,433 7/1971 Schneider ..260/666 PY Ohm Primary Examiner-Delbert E. Gantz [73] Assignee: The B. F. Goodrich Company, New As i tant Examiner--Veronica OKeefe York, NY. Attorney-J. Hughes Powell, Jr. et a1. 22 F1 d: 14 1971 1 June 57 ABSTRACT [21] App]. N0.: 153,096

' 5-V1nylb1cyc1o[2.2.1]hept-2-enes heated in the presence of a titanium catalyst system are isomerized [52] US. Cl. .260/666 PY to 5 2 2 1 h 2 The catalyst [51] hit. Cl C079 5/28 System of this invention comprises a titanium [58] Field Of Search ..260/666 PY pound an alkali meta" and a cyclopentadieny] nesium halide. The catalyst system is highly efficient [56] References cued and capable of rapidly isomerizing 5-vinyl- UNITED STATES PATENTS bicyc1o[2.2. l ]hept-2-enes. 5-Ethylidenebicyclo[2. 2.l ]hept-2-enes are useful comonomers for polymeriza- 3,151,173 9/ 1964 Nyce ..260/ 666 PY tion with l fi such as ethylene and propy1ehe 3,347,944 10/ 1967 Fritz et a]. ..260/666 PY 3,535,395 10/ 1970 Schneider ..260/666 PY 6 Claims, No Drawings PREPARATION OF ETHYLIDENEBICYCLO(2.2. 1)HEPT-2-ENES BACKGROUND OF THE INVENTION Previously known catalysts for the isomerization of 5 -vinylbicyclo[ 2.2. l ]hept-2-ene to S-ethylidenebicyclo[2.2.l]hept-2-ene have not been completely satisfactory. Large amounts of catalyst are often necessary to achieve acceptable rates of isomerization and significant amounts of by-products and poor catalyst efficiency were often noted.

SUMMARY OF THE INVENTION I have now found quite unexpectedly an improved catalytic process for the isomerization of 5-vinylbicyclo[2.2. l ]hept-Z-enes to 5-ethlidenebicyclo[2.2.l ]hept-Z-enes wherein high catalyst efficiencies are achieved. Rapid isomerization rates are realized with the process of the present invention. The increased rate I of isomerization and excellent catalyst efficiencies obtained with the present catalysts are significant since it is now possible to achieve isomerization in very short periods of time employing very low catalyst concentrations. In this manner polymeric by-products formed during the isomerization are minimized and in most instances completely eliminated. The present process utilizes a titanium catalyst comprising a titanium tetravalent compound, an alkali metal and a cyclopentadienyl magnesium halide.

DETAILED DESCRIPTION The isomerization reaction of this invention may be represented as follows:

II. R. It

wherein R is a hydrogen or alkyl group containing from one to four carbon atoms. The process is particularly useful to obtain 5-ethylidenebicyclo[2.2.l]hept-Z-ene (R=H) which is a useful monomer for copolymerization with olefins such as ethylene and propylene.

5-Vinylbicyclo[2.2.l ]HEPT-2-enes employed in the present isomerization process correspond to the structural formula wherein R is a hydrogen or an alkyl group containing from one to four carbon atoms. The present process is particularly advantageous for the isomerization of 5- vinylbicyclo[2.2.l]hept-2-ene (where R=l-I) since this material is readily available from the Diels-Alder addition of 1,3-cyclopentadiene and 1,3-butadiene. Other 5-vinylbicyclo[2.2.l]hept-Z-enes, such as methyl-S- vinylbicyclo[ 2.2. l ]hept-2-enes obtained from the reaction of l,3-cyclopentadiene with piperylene or methyl l,3-cyclopentudienc and butadiene, are just as effectively isomerized by the present process.

While any titanium compound may be used, the particular titanium compounds employed were titanium tetrahalides and titanium alcoholates which correspond to the structural formula wherein X is chlorine, bromine or iodine, R is a hydrocarbon radical containing from one to 12 carbon atoms and more preferably one to eight carbon atoms, such as alkyl, cycloalkyl, aryl and alkaryl groups, and y is an integer from 0 to 4. Excellent results are obtained with titanium tetrachloride, titanium tetrabromide, titanium tetraiodide, C l-l oTiCl (C2H O)zTiCl (C H O) TiCl, tetraethyl titanate, tetra-(isopropyl)titanate, 'tetra-n-butyl titanate, tetra-(2-ethylhexyl)titanate and tetraphenyl titanate. Mixtures of these titanium compounds may also be employed. For example, mixtures of titanium tetrahalides with tetraalkyl titanates are useful as the titanium component in forming the catalyst of the present process.

Any of the available alkali metals may be used in the process, but sodium because of availability and cost, is preferred. To be used most effectively, the sodium should be in finely divided or activated form as in the form of sodium sand, dispersions of sodium in inert solvents as mineral oil, or the isomerization reaction conducted at temperatures above 97.5 C., which is the melting point of sodium, liquid sodium being particularly effective. Activated sodium is well known in organic syntheses.

Any cyclopentadienyl magnesium halide may be used. Excellent results have been obtained with the bromide.

The present catalyst systems are obtained by contacting the titanium compound with the alkali metal and cyclopentadienyl magnesium halide. The catalyst may be prepared prior to use or the individual catalyst components may be mixed in the reaction in the presence of the 5-vinylbicycl0[2.2.l ]hept-Z-ene. If the catalyst system is prepared prior to the isomerization, the components are generally admixed in an inert sol- .vent. This latter method facilitates subsequent storage, handling and charging of the catalyst and is a useful means to control the reaction exotherm.

While large amounts of the titanium compound may be employed, it is an advantage of this invention that small amounts in the range from about millimols per mol 5-vinylbicyclo[2.2.l]hept-2-ene to about 0.1 millimol per mol 5-vinylbicyclo[2.2.l]hept-2-ene may be used. More of the titanium compounds per mol 5- vinylbicyclo[2.2.l ]hept-2-ene can be employed if desired. Excellent results have been obtained when the concentration of the titanium compound is between about 50 millimols and l per mol 5-vinylbicyclo[2.2.l ]hept-Z-ene.

About 2 to 10 mol equivalents each of alkali metal and organo-magnesium compound are normally used per mol equivalent of titanium compound. Excellent results are obtained with about 5:1 mols of sodium and organo-magnesium compound each, per mol of titanium. While a large molar excess of these constituents maybe used, there is no particular advantage in such v vinylbicyclo[2.2.l]hept-2-ene in the presence of the titanium catalyst system. The -vinylbicyclo[2.2.l ]hept-2-ene is generally charged to the reactor and the pre-formed catalyst or the individual catalyst components added thereto. The catalyst or individual catalyst components may be completely charged at the outset of the isomerization or charged continuously as the isomerization progresses. The process may be conducted employing either batch or continuous techniques. Prior to the introduction of the pre-formed catalyst or the titanium compound if the catalyst is to be prepared in situ, an amount of organometallic compound may be charged to the reactor to remove small amounts of undesirable impurities present in the system. The 5-ethylidenebicyclo[2.2. l ]hept-Z-enes can be recovered by fractional distillation or it may be removed continuously throughout the run if continuous operation is employed.

While it is not necessary and bulk reactions are satisfactory, the isomerization may be conducted in an inert diluent such as the aromatic or saturated aliphatic hydrocarbons. Higher boiling saturated hydrocarbons may be employed since they do not interfere with the recovery of the 5-ethylidenebicyclo[2.2.l]hept-2-ene and also permit operation of the process within the desired temperature range without the use of pressure vessels. Useful hydrocarbon solvents include pentane, isopentane, 2,2-dimethylpentane, 2,4-dimethylpentane, 3,3-dimethylpentane, 3-ethylpentane n-hexane, isohexane, 3-methylhexane, n-hexane, n-octane, isooctane, cyclohexane, benzene, toluene, the xylenes, mesitylene and the like or mixtures thereof. If a diluent is employed the ratio of the diluent to 5-vinylbicyclo[2.2. 1 ]hept-Z-ene will generally range between about 1:10 and about :1.

It is not essential that the 5-vinylbicyclo[2.2. 1 ]hept- 2-ene be absolutely pure, however, the presence of large amounts of impurities should be avoided for best results. Small amounts of impurities such as water, alcohols, peroxides and air present in the 5-vinylbicyclo[2.2.l1hept-2-ene or diluent can be tolerated, however, it is preferred they be removed by the addition of a scavenging agent, which in this case can also serve as the modifier, or by some other suitable means. Distillation or sieving of the 5-vinylbicyclo[2.2. l ]hept- 2-ene and diluent prior to use will generally suffice to remove most impurities which seriously impair the catalyst efficiency or promote formation of polymeric materials. It is often advantageous to employ sufficient excess of the alkali metal so that it will also serve as a scavenger to remove impurities such as oxygen, alcohols, water and the like present in the system.

The isomerization process is typically conducted under a dry atmosphere of an inert gas such as nitrogen or argon and may be conducted at atmospheric, sub-atmospheric or super-atmospheric pressure depending on the reaction conditions and diluent employed.

The isomerization process is typically conducted at temperatures above 25 C., up to 300 C. or above. Excellent results, i.e., high catalyst efficiency and a rapid isomerization have been obtained within the temperature range of about 40 to 200 C. The increased rate of isomerization achieved with the present invention permits the isomerization of 5-vinylbicyclo[2.2.l]hept-2- ene to 5-ethylidenebicyclo[2.2.l ]hept-Z-ene on a continuous basis. At room temperature the rate of isomerization, although considerably slower than obtained at elevated temperatures, is nevertheless significant and a reasonable degree of conversion can be achieved.

The invention is illustrated more fully as follows by a representative example that is not intended to limit the scope thereof.-

0.l Mol 5-vinylbicyclo[2.2.l]hept-2-ene prepared by the Diels-Alder reaction of 1,3-cyclopentadiene and 1,3-butadiene as described by A. F. Plate and N. A. Belikova in ZHURNAL OBSHCHEI KHlMll, 30, No. 12, 3945-54 (1960) was charged to a dry argon-purged reactor with 5 millimols of Na, 1 millimol of TiCl and 5 millimols of cyclopentadienyl magnesium bromide added at room temperature with stirring while maintaining an argon purge. The reactor and its contents were heated to C. under an argon atmosphere. The heating was continued for 30 minutes. By vapor phase chromatography it was found that 92 percent of the 5-vinylbicyclo[2.2.l ]hept-2-ene were isomerized to 5-ethylidenebicyclo[2.2.1]hept-2-ene. Another similar run at room temperature for 65 hours resulted in 99 percent conversion of 5-vinylbicyclo[2.2.l ]hept-2-ene.

Copolymers of ethylene, propylene and S-ethylidenebicyclo[2.2.l ]hept-Z-ene are readily prepared by methods known to those skilled in the art. Such elastomers are useful in the manufacture of tire carcasses and sidewalls.

lclaim:

1. A process for the isomerization of 5-vinylbicyclo[2.2. l ]hept-Z-enes to 5-ethylidenebicyclo[ 2.2. l ]hept-2-enes which comprises contacting a S-vinylbicyclo[2.2. l ]hept-2-ene of the formula wherein R is a hydrogen or an alkyl group containing from one to four carbon atoms with a catalyst formed by mixing 1 a titanium compound of the formula wherein X is chlorine, bromine or iodine, R is a hydrocarbon radical containing from one to 12 carbon atoms, and y is an integer from 0 to 4, or mixture thereof, (2) an alkali metal and (3) a cyclopentadienyl magnesium halide.

2. The process of claim 1 wherein the isomerization is conducted at a temperature between about 40 C. and 300 C. with about 2 to 10 mol equivalents of (2) and (3) per mol equivalent of l 3. The process of claim 2 wherein the 5-vinylbicyclo[2.2.l1hept-2-ene is 5-vinylbicyclo[2.2. l ]hept- 2-ene.

4. The process of claim 3 wherein (l) is TiCl (2) is sodium and (3) is cyclopentadienyl magnesium bromide.

5. The process of claim 4 with about 20 millimols to 0.001 millimol of (1) per mol 5-vinylbicyclo[2.2.l ]hept-2-ene and about 2.25 to 5 mol equivalents each of (2) and (3) per mol equivalent (l).

6. The process of claim 5 wherein about 5 millimols to 0.01 millimol l per mol 5-vinylbicyclo[2.2. l ]hept- 2-ene is employed. 

2. The process of claim 1 wherein the isomerization is conducted at a temperature between about 40* C. and 300* C. with about 2 to 10 mol equivalents of (2) and (3) per mol equivalent of (1).
 3. The process of claim 2 wherein the 5-vinylbicyclo(2.2.1)hept-2-ene is 5-vinylbicyclo(2.2.1)hept-2-ene.
 4. The process of claim 3 wherein (1) is TiCl4, (2) is sodium and (3) is cyclopentadienyl magnesium bromide.
 5. The process of claim 4 with about 20 millimols to 0.001 millimol of (1) per mol 5-vinylbicyclo(2.2.1)hept-2-ene and about 2.25 to 5 mol equivalents each of (2) and (3) per mol equivalent (1).
 6. The process of claim 5 wherein about 5 millimols to 0.01 millimol (1) per mol 5-vinylbicyclo(2.2.1)hept-2-ene is employed. 